西藏羊八井废弃地热热井的细菌多样性

Bacterial diversity of disused thermal vents in Tibetan Yangbajing Region

摘要:

【目的】旨在研究羊八井热田两废弃地热热井沉积物及热水中的细菌多样性。【方法】采用非培养分子分析技术分别构建了热井A沉积物A样、水样A以及热井B沉积物B样总DNA的16S rRNA基因文库，并对每个文库中随机挑选的克隆子进行扩增rDNA限制性酶切片段分析（amplified ribosomal DNA restriction analysis, ARDRA），分别选取文库中不同分类单元的阳性克隆子进行测序，将所得到的数据与国际基因数据库GenBank 的序列进行相似性比较并构建系统发育树。【结果】热井A和热井B的细菌类群大多为典型的栖热细菌，均以变形菌（Proteobacteria）为优势类群（在热井A沉积物A中为41.08% 、在水样A中为38.00%，以及在热井B的沉积物B中为42.57%，下同），以恐球菌－栖热菌（Deinococcus-Thermus）为亚优势类群（10.71%、20.00%、21.30%）；此外两热井沉积物中均发现热泉中比较少见的且为亚优势类群的酸杆菌（Acidobacteria）(在热井A沉积物A中为16.07%、在热井B的沉积物B中为19.15%)，热井A沉积物中第三个亚优势类群为壁厚菌门(Firmicutes)的真杆菌（Eubacterium sp.）（14.28%）；水样A中则没有检测到酸杆菌，而以产水菌门（Aquificae）的产氢杆菌属（Hydrogenobacter）为另一亚优势类群(16.00%)。此外两热井中均检测到绿弯菌（Chloroflexi）、蓝藻（Cyanobacteria）以及噬纤维菌-屈挠杆菌-拟杆菌群 (Cytophaga-Flexibacter-Bacteroides，CFB group)等类群的细菌。【结论】通过与文献比较分析，发现羊八井热田中细菌类群大多为典型的栖热细菌，如恐球菌－栖热菌、产水菌、绿弯菌、蓝藻以及candidate division OP类群的微生物等；但是尚有一些不常见的细菌类群如弧菌（Vibrio sp.）、Bacteriovorax sp.、未培养的酸杆菌和Holophaga（uncultured Holophaga/Acidobacterium）和未确定的疣微菌（Unidentified Verrucomicrobium）等，羊八井热田地热的开发变迁和地下冷热水交融可能与细菌类群的复杂性有关。

Abstract:

[Objective] To study the bacterial diversity in sediment and water from two disused thermal vents in Yangbajing, Tibet, China. [Methods] We constructed 16S rRNA gene libraries of the total DNA from three samples. Sediment sample A and water sample A were from thermal vent A. Sediment sample B was from thermal vent B. Positive clones from the libraries were analyzed randomly by amplified ribosomal DNA restriction analysis. Positive clones’ sequences of every Operational Taxonomic Units from libraries were determined, and sequence data were submitted to GenBank and contrasted to those known sequences. Phylogenetic trees were built up by using MEGA4.0 program. [Results] Most of bacteria communities of the two thermal vents were typical thermophilc inhabitants, the predominant proteobacteria communities were found in thermal vent A and thermal vent B (ratios in sediment A, water sample A and sediment B were 41.08%, 38.00% and 42.57%) One of the sub-predominant bacteria communities, Deinococcus-Thermus, was found in thermal vent A and thermal vent B (ratios in sediment A, water sample A and sediment B were 10.71%, 20.00% and 21.30%). Moreover, one of the sub-predominant bacteria communities, Acidobacteria that was rarely found in hot springs or thermal vents, was present both in sediments of thermal vent A and B (16.07%, 19.15%). The third sub-predominant community in sediment of thermal vent A was Eubacterium sp. (14.28%), belonging to phylum Firmicutes whereas no Acidobacteria was found in water sample A. Instead, Hydrogenobacter, belonging to phylum Aquificae, was another sub-predominant community (16.00%) in water sample A. In addition, Chloroflexi, Cyanobacteria and CFB group (Cytophaga-Flexibacter-Bacteroides) were detected in both thermal vents. [Conclusion] Compared with and contrasted to the references, we found that bacteria communities in Yangbajing thermal field were similar to that in some hot springs and thermal vents around the world but slightly abnormal. Some bacteria communities in thermal vent A and thermal vent B were not very popular, such as Vibrio sp., Bacteriovorax sp., Holophaga/Acidobacterium, Verrucomicrobium.